Sump pump air lock question

I have a submersible sump pump and a battery backup. I drilled a 1/8 in hole in my discharge pipe about 2 in up from the pump casing, but below the check valve, a $25.00 brass spring loaded check valve. I did this because everyone says you need to do that to prevent air lock. When I run the system this way it gurgles when the pump shuts off. If I assemble the system without the air lock holes, it does not gurgle and it runs beautifully silent.

The sump basin never empties completely. In other words, the pump never, never sucks any air. If the pump inlet is always submerged, how is any air going to get in to produce air lock? I'd rather run it without the vents/holes because its a very active sump and the bedroom is right above it. Am I safe if, like I say, the pump never has the opportunity to suck air. I mean, I could understand if the pump basin went dry, but it never will, because it never has in the 15 years I've serviced it.